Though in recording apparatus or the like, taking out paper sheet by sheet from a stack has been done for a long time, because the force acting between a sheet of paper to be separated and the remaining sheets is very unstable there has been a problem that not only one sheet, but two sheets or three sheets or more together are separated, or nothing is separated.
Several methods have been deviced for solving this problem but the best method is not found yet so far.
Conventional ways of separating papers in the piled state one sheet by one sheet are classified largely into two kinds, a method to utilize friction of a rubber roller or the like, and another method to utilize suction force of air.
The method to utilize the friction of a rotating rubber roller is one to utilize difference between friction of the rubber roller and the paper and friction between the paper to be separated and the next paper, at the time the rotating rubber roller is pressed to the first paper.
However, in such method the above-mentioned difference of friction is regulated by surface condition of the rubber roller or the like and contact pressure at contacting of the rubber roller to the paper, and because of change of the surface condition as time clapses or because of decrease of the friction due to a sticking of fiber of the paper onto the surface of the rubber roller as a result of friction, the friction between the rubber roller and the paper becomes unstable. Also, since elasticity of the piled paper changes responding to the way the paper has been handled, the contact pressure is difficult to keep constant with respect to change of the piled amount; on the other hand when the contact pressure is made large in order to relatively decrease variation in the amount of the contact pressure, then the paper often is broken due to friction. Also, in order to supplement the unstability of the difference of friction, there has been devised an apparatus to return the second or subsequent paper, but such device becomes very complicated.
On the other hand, though in case of utilizing the suction force of the air there is an advantage that there is almost no effect of the friction force, when the paper is vertically separated a vacuum is produced between the first paper and the next paper and it, too, receives the effect of the vacuum. That is, most devices which utilize the suction have such configuration as to press a suction chuck to the uppermost paper and to bring up the chuck in an upward or slant upward direction, and in this method the difference of force between the force to suck the paper and the force which is generated at the separation of the paper and acts in a direction to hinder the separation, thus becoming a problem. Although by making the force to suck the paper large, the effect of separating the paper can be increased, it is necessary to make the apparatus large in order to increase the suction force, and, for some kinds of paper, two or more papers becomes sucked up at the same time, so there is a necessity to provide means to forcibly drop the second and subsequent ones and the apparatus becomes complicated.